Pump control with line loss compensation



Nov. 26, 1 946. N s. F. HUNT PUMP CONTROL WITH LINE LOSS COMPENSATION Fi1 ed March 6, 1944 INVENTOR.

.5522777 Flinn atnted Nov. 26, 1946' PUMP CONTROL WITH'LINE LOSS COMPENSATION Scott F.

Hunt, Meriden, Conm, assignor to Chandler-Evans Corporation, South 'Meriden, Conn., a corporation of Delaware Application March 6, 1944, Serial No. 525,160

6 Claims.

This invention relates to means for maintaining a constant pressure in a fluid supply line at a point remote from a pressure creating device.

More particularly the invention relates to a device or means for maintaining the pressure within the feed line of an' aircraft engine at constant pressure at the carburetor intakes when they are at a distance from the fuel pump.

A feature of the invention that enables the above object to be accomplished is that a variable pressure is applied to the pump relief or by-pass valve so that when the pressure at any predetermined point in the delivery line of the pump varies, the pressure delivered by the pump may be varied to maintain the pressure at the predetermined point constant.

Another object of the invention is to provide a pressure amplifier at the point in the line desired to be maintained at constant pressure so that a variation in pressure at this point may be converted into an amplified pressure change and this latter pressure applied to supplement the loading of the fuel pump by-pass valve.

With the above and other objects in view the invention may include the features of construction and operation set forth in the following specification and illustrated in the accompanying drawing.

,- amplifier in its delivery line at a point remote from the pump.

In the above-mentioned drawing there has been shown but one embodimentof the invention which is now deemed preferable, but it is to be understood that changes and modifications may be made within the scope of the appended claims without departing from the spirit of the invention.

Briefly, and in its preferred aspect, the invention may include the following principal parts: First, a fuel pump which may be of standard type having a relief valve incorporated therein, the pressure acting against which may 'be supplemented by increasing or decreasing the pressure above a flexible diaphragm connected thereto; second, a pressure amplifier comprising Sylphon bellows, one within the other, the outer one of whichis connected to the delivery line of the pump at the point hereinafter referred to as the control point, desired to be maintained at a the valve H.

I constant pressure, and the inner one of which is directly connected to the space within the fuel pump above the relief valve diaphragm.

In the operation of fuel pumps which normally are set for a predetermined pressure, the delivery point of the pumped fuel may be at a considerable distance from the pump and subject, there'- fore, to a pressure drop due to the velocity of flow through the interconnecting conduit. With variations of velocity within the delivery conduit this drop in pressure may vary substantially. It is therefore an object of the invention to provide simple but eflicientmeans whereby the pressure at any control point in the delivery conduit of a pump can be maintained at constant pressure under varying conditions of flow through the conduit.

Referring more in detail to the figure of the drawing, it will be seen that a pump Ill of the rotating radially movable vane type is provided which may be rotated by any means (not shown) In order to control the pressure delivered by this pump a relief or by-pass valve l I is biased toward closed position by a spring l2, the pressure of which may be adjusted as required.

In the form of pump shown in the drawing a flexible diaphragm I3 is provided in a portion of the pump casing against which the spring l2 operates so that the diaphragm l3 forms a flexible seal for the pump and permits movements of The space within the casing of the pump Ill above the diaphragm I3 is closed as by means of a bonnet member I4 and a cap member l5 threadedly attached to the upper portion of the bonnet l4. To vary the pressure of the spring l2 acting on the diaphragm l3 and by-pass valve II the upper end of the spring l2 bears against a pressure plate l6 suitably guided within the bonnet member ll, the position of which may be varied by adjustment of a screw I'I.

At the control point, a pressure amplifier 20 is provided of the multiple Sylphon bellows type. It will be noted that there are two flexible metal bellows 2| and 22. one within the other, the space within the outer bellows 2! being connected directly to the delivery pipe 23 by means of a branch conduit 24. Enclosed within this bellows is the second bellows 22 of much smaller diameter than the first and this bellows has its interior space directly connected by a conduit 25 extending to the-space within the pump casing Ill .and directly above the flexible diaphragm IS. A spring 26, the pressure of which may be varied by adjustment of screw 21, presses against the upper surface of the inner'and outer bellows to vary the pressure acting thereon. Movement of the outer bellows 2| by variations of pressure in discharge conduit 23 causes the inner bellows 22 to -move correspondingly. Both bellows have 60 their end walls attached together and are free respondingly increased ner bellows and ressure above diaphragm line due to the increased flow higher pressure. By properly to expand and contract by movement upward and downward of their upper ends against the pressure of spring 26.

, It will be seen from the a slight reduction in charge line 23 of the pump will reduce the pressure within the outer bellows 2| and cause this above description that pressurewithin the dismember to correspondingly compress the inner I bellows 22 which will increase the. pressure therein. This increase in pressure within bellows 22 will act directly aphragm l3 of the pump. This increased pressure upon the flexible diap agm I3 will therefore hold down the bypass valve II with a corpressure and thus cause the pump II) to correspondingly increase its delivery pressure. Similarly when the pressure at the control point increases the capacity of the outer bellows will increase and force the inner bellows to expand. This movement of the inner bellows 22 decreases the pressure within the inreduces the-pressure acting on the flexible diaphragm 13. The discharge pressure will therefore be reduced proportionately to the increased pressure at conduitfl.

The area at the free end of bellows 2| on which bellows acts upwardlypressure above the diaphragm l3. For example, point decreases, the l3, and hence the if the pressure at the control upon the 'flex'ible dimatic means will charge pressure, an expansible chamber having cating said control pressure to said chamber to I vary said pump discharge pressure in a sense oppressure at the control point pump discharge'pressure, is increased by a greater amount.- This greater increase in the pump discharge pressure not only counteractsthe original change in pressure at the control point, but also counteracts the increased friction losse in the therethru at the adjusting the screws H and 21, the pressure at the control point may beheld substantially-constant.

Y control pressure varying oppositely with vari- The variations in pressure within the conduit 1 23 therefore cause variations in pressure within the valve casing above the flexible which will add to or subtract from the pressure of the spring l2 acting on the valve H and thus will vary the the pump.

I claim:

1. A pressure maintaining device for pump discharge conduits comprising, a pump having a pressure controlled by-pam valve, means to adjust the pressure acting on said valve, pneumatic means to supplement the pressure acting pressure amplifier connecton said valve, and a ed to said conduit at a point remote from said pump to vary the pressure of said pneumatic means with variations of pressure within said discharge conduit.-

diaphragm is pressure of the fluid delivered by 2. A pressure maintaining device for pump discharge conduits comprising, a pump having a pressure controlled by-pass valve, means to adjust the pressure acting on said valve, pneumatic means to supplement the pressure. acting on said valve, and a pressure, amplifier connected to said conduit at a point remote from said pump to increase the pressure or said pneumatic means proportionately to a reduction of pressure within said discharge conduit.

as to compensate for the pressure drop in said thereby to maintain a. substantially constant pressure at said point.

3. A pressure maintaining device for pump discharge conduits comprising, a pump having a pressure controlled by-pass valve, means to adjust the pressure acting on said valve, pneumatic means to supplement the pressure acting on said valve, and a pressure amplifier connected to said conduit at a point remote from said pump, said amplifier having a bellows subjected sure therein, whereby the pressure ot'sald pn ube varied :with variations of pressure within said discharge line. 1 v

4. Apparatus for regulating the discharge" pressure or a pump which discharges thru a long conduit, comprising a-reliei valve subject to the pump discharge pressure,,a spring biasing said relief valve closed against the action of said disa movable wall connected to said valve so that the pressure in said chamber acts on said valve in opposition to said responsive to the pressure in said conduit at a point remote from said pump for producing a control pressure greater than said conduit pressure and for varying said control pressure oppositely. and proportionally with variations in said conduit pressure, and means for communiposite to the variations in said conduit pressure so as to compensate for the pressure drop in said conduit between said pump and said pointand thereby to maintain a substantially constant pressure at said point.

5. Apparatus for regulating the" discharge V pressure of a pump which discharges thru a long conduit, comprising a relief valve subject to the pump discharge pressure, aspring biasing said relief valve closed against the action of said discharge pressure, an expansible chamber having a movable wall connected to said valve so that the pressure in saidcham-ber acts on said valve in opposition to said discharge pressure, means responsive to the pressure in said conduit at a point remote from said pump for producing a in a sense opposite to the .variations in said con-- t) duit pressure so as'to compensate for the pressure drop in said conduit between said pump and, said point and thereby to maintain a substantially constant pressure at said point.

6. Apparatus for regulatingv the discharge pressure of a pump which discharges thru a long conduit, comprising a relief valve subject to the pump discharge pressure, a-spring biasing said relief valve closed against the action of said discharge pressure, an expansible'chamber having a movable wall connected to saidv valve for applying'a variable, control force thereto, means, responsive to the pressure in said conduit at a point remote from said pump for producing a control pressure varying as a function or said conduit pressure; and means for communicating said control pressure to said chamber to vary said pump "discharge pressure in a sense opposite to the variations in said conduit pressure so conduit between said pump and said point and scorr F.

discharge pressure, means 

